1. Field of the Invention
The present invention is related to a diagnosis assisting apparatus, a diagnosis assisting method, and a storage medium, in which a diagnosis assisting computer program is recorded, that assist diagnosis by automatically analyzing the functions of organs using three dimensional image data, and by displaying index values which are obtained as a result of the analysis.
2. Description of the Related Art
There are known apparatuses that aid image diagnosis by radiologists, that analyze the states and motions of organs of subjects, based on three dimensional data obtained by imaging the subjects, and display the analysis results in a form suited for diagnosis on screens. A function that calculates evaluation indices of cardiac function (amount of myocardial wall activity, variations in myocardial wall thickness, etc.) based on three dimensional data obtained in temporal sequences is known as an analyzing function of cardiac activity. These evaluation indices are calculated for each of a plurality of cross sections, which are set to be perpendicular to an axis that passes through the base of the heart (the upper portion of the heart where blood vessels are connected) to the apex of the heart (the lower portion of the heart shaped as an apex). The calculated evaluation indices are generally displayed three dimensionally to match the shape of the heart. Meanwhile, bulls eye images, in which the evaluation indices for each cross section are arranged along the circumference of concentric circles having different radii, are known as a method for two dimensionally displaying the analysis results (refer to Japanese Unexamined Patent Publication No. 2009-018005, for example).
In addition, a function of displaying images of coronary arteries overlapped on the bulls eye images has also been proposed (refer to Japanese Unexamined Patent Publication Nos. 2005-027999 (corresponding to U.S. Patent Application Publication No. 20050008209) and 2008-253753 (corresponding to European Patent Publication No. 2130490), for example). Abnormalities in cardiac activity (such as myocardial infarction) are often caused by abnormalities (such as occlusions) of the coronary arteries that supply oxygen and nutrients to the myocardial muscles. Therefore, by observing the shapes of the coronary arteries along with the evaluation values of cardiac functions, judging which coronary artery is the cause of an abnormality in cardiac function can be facilitated.
A method, in which a myocardial region is sectioned into a region close to the right coronary artery (RCA), a region close to the left anterior descending artery (LAD), and a region close to the left circumflex coronary artery (LCX), and cardiac functions are analyzed in units of the sectioned regions, has been proposed. The regions are commonly sectioned by drawing boundary lines having predetermined shapes at predetermined positions. In addition, a method has also been proposed that determines optimal boundaries for each subject, by applying the Voronoi algorithm (M. A. Termeer et al., “Patient-Specific Coronary Artery Supply Territory AHA Diagrams”, TU Wien, 12th Annual SCMR Scientific Sessions—2009, pp. 164-165, January 2009; http://www.cg.tuwien.ac.at/research/publications/2009/termeer-2 009-scmr/). According to these methods, coronary arteries which are suspected to have abnormalities can be specified to a degree, based on the analysis results of each of the regions.
In the method that sections the myocardial region and analyzes the sectioned regions, new index values (for example, an average value of evaluation values within the sectioned regions) for evaluating cardiac functions in units of the sectioned regions are derived, and whether each sectioned region is functioning properly is judged based on the index values. However, there are cases that cardiac muscles in the vicinities of the boundaries of the sectioned regions receive oxygen and nutrients from two to three coronary arteries. Therefore, the evaluation values in the vicinities of the boundaries do not necessarily reflect the influence that individual coronary arteries impart on myocardial function. For this reason, it is not preferable to employ all of the evaluation values which are included in the sectioned regions during calculation of the index values, from the viewpoint of accuracy of analysis.